面向片上电泳分离的电动流体数值计算研究

针对片上电泳分离的特点和需求,分析了片上电泳分离的机理,编制了电泳分离过程的数值计算程序,建立了面向片上电泳分离的电动流体计算平台。在不规则微通道内生成贴体同位网格,并用链导法对控制方程进行转换;采用有限体积法计算微通道内电场分布、缓冲溶液流场分布和电泳分离组分分布;对流场计算,采用动量插值方法解决求解过程中压力和速度失耦问题;采用QUICK格式离散组分传输的对流项,减小了数值耗散引起的“虚假区带增宽”。给出了微通道弯曲结构内电泳分离过程计算结果,验证了计算的有效性和可信性。     

The effect of non-orthogonal grids on spray and air flow predictions

This paper describes the effect of non-orthogonal grids on both spray and air flow predictions, and the effect of higher order convection scheme on inclined grids. In order to assess the effect of non-orthogonality of grids a number of different grid cases are generated, and applied to the same conditions of injected sprays. The effects on the free/wall spray penetration and Sauter mean diameter (SMD) are discussed. The results show that the numerical error is increased with increasing non-orthogonality, and that Hybrid is better than QUICK for the calculation of sprays on inclined grids. For the calculation of the spray injection, which has always large gradient regions at the front end, adaptive grids following the direction of spray/ gas flow might be required.     

A simple approach to analyze process damping in chatter vibration

This paper investigates how changes in chatter amplitude and frequency depend on process damping effect in dynamic turning process. For this purpose, the two degrees of freedom (TDOF) cutting system was modeled, and for an orthogonal turning system, the process damping model with a new simple approach was developed. To further explore the nature of the TDOF cutting model, a numerical simulation of the process was developed by this model. This simulation was able to overcome some of the weaknesses of the analytical model. The equations of motion for this cutting system were written as linear and nonlinear in the τ-decomposition form. The variation in the process damping ratios for different work materials was simply obtained by solving the nonlinear differential equations. A series of orthogonal chatter stability tests were performed for the identification of dynamic cutting force coefficients, using AISI-1040, Al-7075, and Al-6061 work materials, at a constant spindle speed. Finally, the experimental results were analyzed and compared with the simulation model, and it was observed that the results obtained through the experiments comply with the simulation model results.     

A bulk-flow analysis of static and dynamic characteristics of floating ring seals

The bulk-flow model was used to calculate the static and the dynamic characteristics of floating ring seals because the solutions based on the numerical integration of the complete Navier–Stokes equations can be very time consuming. A steepest-descent method is used to find the seal's equilibrium position efficiently. The bulk-flow model is governed by three partial differential equations on eccentric working conditions. A finite-difference scheme has been used to solve the nonlinear governing equations. Compared to Nelson and Nguyen's fast fourier transform method, this scheme has better consistency. Perturbation analysis of the flow variables yields a set of zeroth and first-order equations. The SIMPLE algorithm is used to integrate the system of bulk-flow equations. Comparisons of the numerical predictions (lock-up eccentricity ratio, leakage flow rate and rotordynamic coefficients) with Ha's results, which were formulated using the Fourier series, and experimental data are presented subsequently.     

Numerical Study of Two-Phase Mechanical Seal Stability

The axial dynamic stability of two-phase mechanical seals has been studied theoretically. A numerical model featuring thermoelastic deformations, asperity contact, and squeeze film effects, was developed and implemented in a computer program to predict the transient behavior of two-phase seals. The governing system of ordinary differential equations is very stiff and is time-integrated using a scheme based on singular perturbation concepts. The model has been used to predict the dynamic behavior of a seal, with axial perturbations initiated from various operating conditions. Both popping open and oscillatory motion have been encountered. Results show that equilibrium points with positive stiffness are stable if the total face coning is positive. However, if the total coning is negative the point is unstable, even if the stiffness is positive. Equilibrium points with negative stiffness are unstable.     

Fuel spray dynamic characteristics of GDI high pressure injection system

In order to improve the fuel consumption and exhaust emission for gasoline engines,gasoline direct injection (GDI) system is spotlighted to solve these requirements.Thus,many researchers focus on the i...     

Vibration analysis on plates by orthogonal polynomials

This paper presents vibration analysis of plates by the Rayleigh-Ritz method with orthogonal polynomials derived by the Gram-Schmidt Process as displacement functions, and Gauss-Legendre Quadrature as an integration scheme. A computer program was developed and numerical results by this computation were in good accord with those obtained by using other beam functions. Furthermore, the present method was shown to resolve various problems encountered in the application of existing methods.     

Multi-domain structural-acoustic coupling analysis using the finite element and boundary element techniques

A new approach to analyze the multi-domain acoustic system divided and enclosed by flexible structures is presented in this paper. The boundary element formulation of the Helmholtz integral equation is used for the internal fields and the finite element formulation for the structures surrounding the fields. We developed a numerical analysis program for the structural-acoustic coupling problems of the multi-domain system, in which boundary conditions such as the continuity of normal particle velocity and sound pressure in the structural interfaces between Field 1 and Field 2 are not needed. The validity of the numerical analysis program is verified by comparing the numerical results with the experimental ones. Example problems are included to investigate the characteristics of the coupled multi-domain system.     

求解非定常不可压湍流的SMAC隐式方法

基于简化标记和单元(Simplified marker and cell,SMAC)方法,发展一种在任意曲线坐标系中求解三维非定常不可压湍流Reynolds时均方程的隐式数值方法。控制方程包括以逆变速度为变量的动量方程、压力Poisson方程和k–e 湍流模型方程,控制方程的离散在三维标记和单元(Marker and cell,MAC)交错网格系统中进行。为提高方程数值计算的稳定性,动量方程、k方程和e 方程对流项离散均采用Chakravarthy-Osher总变差衰减(Total variation diminishing,TVD)格式。动量方程、k方程和e 方程离散后的代数方程组采用循环三对角阵算法(Cyclic tridiagonal matrix algorithm,CTDMA)方法进行求解,Poisson方程离散后的代数方程组采用Tschebyscheff超线性松弛(Successive linear over relaxation,SLOR)方法交替方向迭代求解。用该方法自编程序对简化后的射流放水阀内非定常流场进行数值模拟,计算结果和试验结果吻合。     

Numerical model for thermal hydraulic analysis in cable-in-conduit-conductors

The issue of quench is related to safety operation of large-scale superconducting magnet system fabricated by cable-in-conduit conductor. A numerical method is presented to simulate the thermal hydraulic quench characteristics in the superconducting Tokamak magnet system. One-dimensional fluid dynamic equations for supercritical helium and the equation of heat conduction for the conduit are used to describe the thermal hydraulic characteristics in the cable-in-conduit conductor, The high heat transfer approximation between supercritical helium and superconducting strands is taken into account due to strong heating induced flow of supercritical helium, The fully implicit time integration of upwind scheme for finite volume method is utilized to discretize the equations on the staggered mesh, The scheme of a new adaptive mesh is proposed for the moving boundary problem and the time term is discretized by the-implicit scheme, It remarkably reduces the CPU time by local linearization of coefficient and the compressible storage of the large sparse matrix of discretized equations. The discretized equations are solved by the IMSL The numerical implement is discussed in detail, The validation of this method is demonstrated by comparison of the numerical results with those of the SARUMAN and the QUENCHER and experimental measurements.     

A high resolution and bounded convection scheme

A high resolution and bounded convection scheme is proposed for the simulation of steady incompressible flows with finite volume method. The scheme is formulated on a nonuniform, nonorthogonal grid so as to be applicable to the simulation of practical engineering problems. The relative performance of the scheme is evaluated through applications to the test problems. The results of numerical experiments show that the proposed scheme yields similiar solutions which are as good as those obtained with the QUICK scheme, but without exhibiting the physically unrealistic overshoots and undershoots.     

A thermoelastic-plastic large deformation model for orthogonal cutting with tool flank wear—Part I: Computational procedures

A coupled model of a thermoelastic-plastic material undergoing large deformation during orthogonal cutting with a pre-honed land simulating tool flank wear is constructed. A coupled method in which deformation is analysed using the finite element method and transient heat transfer with a finite difference method including special numerical techniques is developed. The cutting tool is incrementally advanced forward in a step-by-step process from the incipient stage of tool-workpiece engagement to a steady state of chip formation. A chip separation criterion based on the critical value of the strain energy density is introduced into the analytical model and a scheme of twin node processing is presented for chip formation in this model. A numerical technique of gradually reducing displacement was developed to deal with the generation of new nodes of contact with the tool flank. Convergence criteria and techniques are also developed in this paper.     

Study of unsteady fluid-dynamic forces acting on a flexible cylinder in a concentric annulus

The unsteady fluid-dynamic forces, generated by a flexural motion in axial (laminar) flow, have been formulated based on a collocation finite-difference method for concentric configurations, in connection with the flow-induced vibration problem. Based on the numerical method, the governing equations of the unsteady flow, obtained from the appropriate Navier-Stokes and continuity equations, redcuced to a system of algebraic equations leading to a block-tridiagonal system. To obtain a solution of the system, the LU decomposition method is used considering the factorization scheme. This numerical method is capable of taking fully into account unsteady viscous effects and of predicting viscous forces rigorously rather than approximately, in contrast with existing theories. In order to validate the numerical approach, semi-analytical approaches have been developed for estimating the fluid-dynamic forces. The numerical results are compared to the analytical results and good agreement was found. The contribution of unsteady viscous damping forces to the overall unsteady forces is significant for low values of the oscillatory Reynolds number, expecially in very narrow annuli.     

GPU-based collision analysis between a multi-body system and numerous particles

The use of a graphics processing unit (GPU) is an ideal solution for problems on data-parallel computations. The serial CPU-based program for collision analysis between a multi-body system and numerous particles is rebuilt as a parallel program that uses the advantages of a GPU. In this study, a GPU is used to effectively perform multi-body dynamic simulation with particle dynamics. The multibody system has 20 circular objects, 19 spring-damper force elements, and 2 revolute joints. The motion equations are formulated using the Cartesian coordinate system, and the implicit Hilber-Hughes-Taylor integration algorithm is used for the integral equation. To detect collisions between a multi-body system and particles or between particles, a spatial subdivision algorithm and a discrete element modeling are used. The developed program is verified by comparing the results with ADAMS. The numerical efficiencies of the serial program using CPU and the parallel program using GPU are compared according to the number of particles. The results show that the greater the number of particles, the more computing time can be saved. For example, when the number of particles is 900, the computing speed of the parallel analysis program is about five times faster than that of the serial analysis program.     

4种脱硫喷嘴雾化特性对比试验

对目前湿法烟气脱硫系统中常用的4种机械式雾化喷嘴进行了雾化试验,采用高速数码摄影法对4种喷嘴在不同压力下的喷雾状况进行测试,并用ImageJ软件处理,得到各喷嘴在不同工况下的粒径、粒径分布和雾化角等特性。研究结果表明:4种喷嘴雾化粒径随液压的增大呈减小趋势,其中螺旋喷嘴雾化粒径最小,扇形喷嘴雾化粒径最大;螺旋喷嘴、空心锥喷嘴和扇形喷嘴的雾化角随液压增大变化不大,较为稳定,实心锥喷嘴雾化角随液压增大而增大,螺旋喷嘴与扇形喷嘴的雾化角较大,空心锥喷嘴的雾化角最小;各喷嘴在小于0.2MPa的液压下粒径分布不均匀,当达到0.2MPa后粒径分布较为均匀。综合结构特点和雾化特性,螺旋喷嘴较适用于火电厂湿法烟气脱硫系统。     

奇点分析单元法在断裂问题中的应用

将裂纹应力计算问题导向哈密顿体系，利用分离变量法及本征函数向量展开等方法，推导出裂纹尖端的尖力奇性解的计算公式。结合变分原理，提出一种解决应力奇性计算的奇点分析单元。将此分析单元与有限元法相结合，可以进行某些断裂力学或复合材料等应力奇性问题的计算及分析。数值计算结果表明，该方法具有精度同，使用十分方便、灵活等优点，是哈密顿体系优越性的一次具体体现。     

弹性支承体与旋转叶片耦合系统的固有频率分析

应用多体系统动力学理论建立弹性支承体与旋转叶片耦合系统的动力学方程 ,在系统稳定运动状态下 ,对耦合系统的动力学方程进行线性化处理 ,然后计算其系统固有频率 ;分析弹性支承体变形对系统固有频率的影响     

Numerical study on the improvement of resistance performance for fast-ferry with transom appendage

In recent, stern wedges and stern flaps are installed for the improvement of propulsion and resistance performance of fast-ferry. For example, U.S. Navy has achieved the development of stern wedges and stern flaps for destroyer to enhance powering performance. It is generally known that stern wave systems as well as bow wave systems play an important role in the wave making resistance performance for fast-ferry. The bow diverging wave system has been usually simulated by an interface tracking method (ITM). However, it is difficult to apply the ITM to the numerical simulation of the stern wave and spray phenomenon because of over-turning wave and wave-breaking. Therefore, to solve this problem an interface capturing method (ICM) is introduced. In the present study, a numerical method with the ICM is developed to evaluate the resistance performance of fast-ferry. Incompressible Navier-Stokes and continuity equations are employed in the present study and the equations are discretized by Finite Difference Method in the general curvilinear coordinate system. CIP (Constrained Interpolated Profile) method is used for the discretization of convection terms, respectively. The free surface location is determined by level set method. In order to validate the numerical method, numerical simulations for Wigley hull are performed and their results are compared with experimental results. Several numerical simulations of ship waves for fast-ferry are performed to find advantages of appendage installation. Through those simulations, the computed results, such as wave profile and resistance coefficient, are compared with the measured results which are achieved from Samsung Ship Model Basin (SSMB). The effects of transom appendage on the resistance performance are discussed with the computed results in this study.     

Pulsatile flow of viscous and viscoelastic fluids in constricted tubes

The unsteady flow of blood through stenosed artery, driven by an oscillatory pressure gradient, is studied. An appropriate shape of the time-dependent stenoses which are overlapped in the realm of the formation of arterial narrowing is constructed mathematically. A msathematical model is developed by treating blood as a non-Newtonian fluid characterized by the Oldroyd-B and Cross models. A numerical scheme has been used to solve the unsteady nonlinear Navier-stokes equations in cylindrical coordinate system governing flow, assuming axial symmetry under laminar flow condition so that the problem effectively becomes two-dimensional. Finite difference technique was used to investigate the effects of parameters such as pulsatility, non-Newtonian properties and the flow time on the velocity components, the rate of flow, and the wall shear stress through their graphical representations quantitatively at the end of the paper in order to validate the applicability of the present improved mathematical model under consideration.     

基于Matlab的牛头刨床运动学分析及通用仿真软件开发

文中建立了牛头刨床的力学模型,基于分析力学原理推导了牛头刨床的运动微分方程。利用MATLAB软件开发了牛头刨床的通用运动学分析软件,并对牛头刨床的运动学规律进行了数值仿真,为该种机床的优化设计提供了理论支撑。